a) Field of the Invention
The invention is directed to a vacuum leadthrough or vacuum pipe for a part which is mounted so as to be movable and projects from outside a vacuum chamber into a vacuum in the vacuum chamber. The invention is further directed to a vacuum valve with a vacuum pipe of the type mentioned above.
b) Description of the Related Art
Vacuum pipes are used for different applications in which there are movable parts projecting from outside the vacuum into the vacuum. Parts of this type are, for example, manipulators which are used for manipulation carried out in a vacuum from the outside. Vacuum pipes are also used in vacuum valves. A commonly used vacuum valve of this type is the plate valve, as it is called, in which a valve opening is closed by a valve plate fastened to a valve rod. The valve rod is guided by means of a vacuum pipe out of the vacuum, where an actuating device is provided for the valve rod to open and close the plate valve. Vacuum valves of this type are known, for example, from U.S. Pat. No. 5,415,376 A, U.S. Pat. No. 5,641,149 A, U.S. Pat. No. 6,045,117 A, U.S. Pat. No. 5,934,646 A, U.S. Pat. No. 5,755,255 A, U.S. Pat. No. 6,082,706 A and U.S. Pat. No. 6,095,180 A.
Bellows or diaphragm bellows are often used to seal vacuum pipes. Besides linear movements, these bellows also allow tilting movements and are absolutely tight. Bellows are disadvantageous because of their relatively large dimensions, relatively high manufacturing cost and their somewhat time-consuming assembly when installed in the system. Bellows also have relatively large inner surfaces which can result in unwanted depositing of particles that can be released in part when the bellows move. This release of particles can result in impairment of high-purity surfaces, for example, in wafer handling.
When only linear movements in axial direction of the part extending into the vacuum are required, an O-ring can be used in a known manner for sealing between the wall and the part, this O-ring being arranged at the surface of the wall defining the opening so as to contact the outer surface of the part passing through the opening. When this part is displaced, the O-ring slides along the outer surface of the part. Accordingly, friction always occurs in a seal of this kind, resulting in wear of the O-ring and in the release of particles. Further, a lubrication of the seal is usually required.
It is the primary object of the invention to provide a vacuum pipe in which no sliding friction occurs during a linear movement of the guided-through part and which does not require lubrication. A further object of the invention is to provide a vacuum pipe which is constructed in a simple manner and is easy to assemble and maintain. A further object of the invention consists in providing a vacuum pipe which does not cause unnecessary release of particles during a movement of the part that is guided through.
A vacuum pipe according to the invention comprises
an opening in a wall limiting the vacuum, with an inner side facing the vacuum and an outer side at which is provided an annular sealing surface surrounding the opening,
an annular sealing surface at the part projecting through the opening into the vacuum from outside the vacuum,
a sealing arrangement which is provided between the annular sealing surfaces of the wall and of the part and which comprises at least one sealing ring of elastic material, and
a guide device which guides the part relative to the wall and by means of which at least a minimum axial pressing force is maintained on the at least one O-ring in every position of the part resulting in a deformation of the at least one sealing ring such that tightness is ensured, wherein the deformation of the sealing ring changes at least in areas of the sealing ring when the part moves relative to the wall.
A vacuum pipe according to the invention can enable tilting movements of the guided-through part or smaller linear movements of this part or combined tilting and linear movements depending on the construction of the guide device. Examples of guide devices of this kind are described in more detail in the description of the drawings.
The opening in the wall can be circular or can have a different shape. The sealing surface which surrounds the opening in the wall can be circular or can have another circumferentially closed shape, for example, oval or rectangular with rounded comers. The annular sealing surface can likewise be constructed so as to be circular at the part projecting through the opening into the vacuum or can have another circumferentially closed shape, for example, oval or rectangular with rounded comers.
In a preferred embodiment example of the invention, two or more sealing rings of elastic material are provided, an inelastic intermediate ring being arranged therebetween, which intermediate ring has oppositely located lateral surfaces contacted by the sealing rings and forming sealing surfaces. The freedom of movement of the guided-through part can accordingly be increased for linear movements as well as tilting movements.
The various features and constructions according to the invention are indicated in the claims.
Further advantages and details of the invention are described in the following with reference to the embodiment examples shown in the drawings, further aims of the invention following therefrom.